We have synthesized several potent inhibitors of [3-amyloid and other peptide fibrillogenesis containing N-methyl amino acids in alternate positions of sequences homologous to putative aggregation sites. Thus far, we have made inhibitors of 13-amyloid and prion peptide, and have recently synthesized a peptide designed to inhibit aggregation of huntingtin. The overall goal of this research is to understand the forces that promote the binding these inhibitors to Alzheimer's 13-amyloid and related fibrils, in particular, the relative importance of hydrogen bonds involving the peptide backbone, and side chain interactions, including hydrophobic interactions and hydrogen bonds. Specific aim 1 is to determine the modes of interaction between AI3(1-40) and inhibitors ofAI3 fibrillogenesis. We will determine the site of binding and orientation (parallel or antiparallel) between fibrillogenesis inhibitor peptides and AI3(1-40) using solid state NMR spectroscopy, in particular, heteronuclear 15NJ3C-REDOR pulse sequence NMR, with Dr. Robert Tycko of N.I.H. We will also study these peptide interactions and determine the structure of complexes between a fibrillogenesis inhibitor, A13(16-20)m and A13(1-40), using solution state NMR and other biophysical approaches. Specific aim 2 is to understand the modes of association of inhibitor peptides with A_, and to understand the roles of hydrogen bonds, the hydrophobic effect, and conformational rigidity in these interactions. Specific Aim 3 is to examine the role of amphiphilicity in determining the orientation, parallel or antiparallel of t3-sheet fibrils. We hope, with these to resolve a controversy in the AI3 literature. We hypothesize that whereas non-amphiphilic peptides tend to form fibrils with antiparallel [3-sheets, amphiphilic peptides such as A13(1-40) are driven towards forming fibrils with parallel t3-sheets. This hypothesis will be tested using REDOR and other biophysical techniques on short AI3 peptides known to form antiparalM 13-sheet fibrils. We will test the hypothesis that the addition of fatty acids to render these peptides amphiphilic will reverse their orientation to parallel 13-sheets. Specific aim 4 is to examine the ability of a peptide backbone and side chain methylated polyglutaminyl peptide to inhibit aggregation and disaggregate fibrils of huntingtin, and to examine their mode of interaction with huntingtin peptides in vitro and in vivo. These inhibitor designs may be useful for understanding the forces that promote fibrillogenesis in neuro-degenerative diseases, and in designing novel diagnostic or therapeutic agents for these diseases.